The present invention relates to cameras.
In particular, the present invention relates to cameras having adjustable objectives.
The present invention relates to that type of device according to which an objective can be moved along its optical axis without play upon movement of an adjusting member which extends transversely with respect to the optical axis and which can be moved with respect to the objective, this movable adjusting member having an inclined surface engaged by a member which is fixed to the objective and which is urged against the inclined surface by a spring.
With a known construction of the above type the pressure with which the member fixed to the objective acts against the inclined surface of the transversely movable member can be resolved into a pair of vectors, one of which acts in the direction of the optical axis and the other of which is perpendicular thereto. The component of this force which is perpendicular to the optical axis seeks to overcome the frictional forces which are encountered and to return the movable objective-adjusting member toward a position where this movable adjusting member is free of forces acting on the same. Such movement is prevented by mounting the movable member in such a way that it is difficult to move so as to assure the presence of sufficiently great forces of friction to hold the movable member in its adjusted position. This requirement of a relatively great friction for the member which is moved to adjust the objective has a considerable disadvantage in that the adjustment of this movable member under certain circumstances can only be carried out in a non-uniform manner because the so-called stick-slip effect is encountered. In other words this movable member in a conventional construction does not slide smoothly and instead tends at one time to stick and then at another time to slip easily, rendering it difficult to provide a precise adjustment of the objective.